JP2004177832A - Optical filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-quality and more reliable optical filter capable of securing an optical effective area even when it is made small-sized, restraining an optical contamination caused on the optical filter to the utmost without lowering mechanical impact resistance and also easily discriminating a beam splitting direction and the front surface and the back surface of the principal plane of the optical filter so that a required beam splitting pattern is obtained. <P>SOLUTION: In the optical filter 1 having the beam splitting direction where a light beam made incident on the principal plane is split and emitted in a given direction and constituted by applying first chamfering to all the periphery of the end of at least either principal plane on an incident side or that on an emitting side, second chamfering 12 whose chamfering amount is different from the first chamfering 11 showing the beam splitting direction is formed at the end of at least either principal plane on the incident side or that on the emitting side. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to the structure of various optical filters such as an optical low-pass filter used for a video camera and an electronic still camera.
[0002]
[Prior art]
2. Description of the Related Art An image pickup apparatus such as a general video camera and an electronic still camera includes a coupling optical system, a color correction filter such as an infrared cut filter, various optical filters such as an optical low-pass filter, a CCD ( The solid-state imaging devices such as a charge coupled device (MOS) and a metal oxide semiconductor (MOS) are arranged in this order.
[0003]
Among these configurations, the optical low-pass filter filters an optical false signal detected by the imaging device, thereby preventing the image quality of the video camera from being degraded. That is, when a subject having color information (such as lattice fringes) close to the pixel pitch of an imaging device such as a CCD is photographed, a pseudo signal different from the original video information is generated in the imaging device, and the color of the output video is blurred. Moire phenomenon sometimes occurred. An optical low-pass filter is used to block and attenuate a spatial frequency component related to such a pseudo signal. The optical low-pass filter has, for example, a configuration in which at least one or more quartz birefringent plates are used, and an antireflection film is generally applied to a main surface portion exposed on the surface thereof. The incident light is separated into an ordinary ray and an extraordinary ray by the birefringence effect of the crystal to be emitted light, and has a predetermined light beam separation direction and a predetermined separation width on its main surface. In such a crystal birefringent plate, a notch or the like is generally formed at an end of the main surface to clearly indicate the light beam separation direction. (For example, see Patent Document 1).
[0004]
However, such an explicit means requires a separate step of forming a notch, which leads to an increase in cost and a small amount of cracks during processing, which tends to cause cracks and chipping. Was weak. Further, by forming a notch or the like, an optically effective area due to the small size of the optical low-pass filter may not be secured. Furthermore, recently, a square plate shape has been adopted as an optical low-pass filter for an electronic still camera according to the shape of a solid-state imaging device such as a CCD. In this case, in addition to the discrimination of the light beam separation direction of the optical low-pass filter, the discrimination of the front and back main surfaces of the optical low-pass filter (the discrimination between the main surface on the incident side and the main surface on the output side) and the center point of the main surface of the optical low-pass filter is 90 °. The necessity of discriminating between the vertical direction and the horizontal direction when rotated is required. For example, depending on the luminous flux separation pattern of the optical low-pass filter, if the front and back principal surfaces of the optical low-pass filter are arranged incorrectly, the luminous flux separation pattern may be different from that originally required, and the performance of the optical low-pass filter may not be sufficiently exhibited. there were.
[0005]
Further, an imaging device such as a CCD has a relatively wide sensitivity characteristic, and responds to light in a part of the infrared region in addition to light in the visible region. However, in an imaging apparatus used for normal subject photographing, infrared incident light becomes stray light, which causes a decrease in resolution, image spots and unevenness, and adversely affects color reproducibility. In order to eliminate such adverse effects and correct the optical characteristics, the optical low-pass filter includes, for example, an infrared cut filter as a color correction filter. As the infrared cut filter, a member such as a colored glass or a colored resin plate may be attached to the optical low-pass filter or a multilayer infrared cut coat material (hereinafter, referred to as an infrared cut coat) such as Al2O3, TiO2, and SiO2, depending on the application. The optical low-pass filter is formed, and these are combined as needed.
[0006]
However, the infrared cut filter has more irregularities on its main surface than a mirror-finished quartz birefringent plate, and these irregularities may become optical foreign substances. In recent years, the miniaturization of imaging devices such as video cameras has progressed, and the distance from an optical low-pass filter disposed in front of an imaging device such as a CCD has also been shortened. In some cases, the refraction plate was disposed closer to the CCD than the main surface. At this time, the unevenness of the main surface becomes an optical foreign matter, becomes noticeable as noise on the image, and deteriorates the quality of the video output. In particular, when an infrared cut coat is used, it is difficult to determine the front and back sides, and since a multilayer thin film is formed on the main surface of the optical low-pass filter by vapor deposition or the like, the main surface is likely to be uneven, and optical foreign matter It is easy to be.
[0007]
In the production of such an optical low-pass filter, at the wafer stage, necessary optical plates are bonded according to required filtering characteristics, or an infrared cut coat is formed. A so-called multi-cavity cutting method for small-piece cutting has been proposed and put into practical use. Such a manufacturing method has made it possible to reduce the manufacturing cost (for example, see Patent Document 2).
[0008]
However, in the optical low-pass filter manufactured by such a multi-cavity method, the cut ridge at the end of the main surface is sharp, and the ridge is microscopically cracked or chipped in many places. It was often in a state where it could be done. In such a state, there is a high possibility that a part of the optical plate is further chipped or cracked, and the broken pieces or chips adhere to the main surface of the optical plate, that is, the optical information transmitting surface, and become optical foreign substances. was there. Such foreign matter is captured by an image pickup device such as a CCD and causes deterioration in image quality when outputting video. In addition, the sharp state of the ridge may cut other members, and such cutting waste may generate optical foreign matter. For example, an optical low-pass filter is often stored and packed in a resin case and delivered to a customer.However, the optical low-pass filter moves inside the storage case and cuts the inner wall of the resin case at the ridge portion. May adhere to the surface.
[0009]
Further, as an effective technique for suppressing the above-mentioned problem, there has been proposed a configuration in which a ridge formed on an optical low-pass filter is chamfered to solve the problem caused by the generation of the optical foreign matter (for example, Patent Document 3). reference).
[0010]
However, Patent Document 3 does not consider the determination of the light beam separation direction and the determination of the front and back of the main surface of the optical low-pass filter as described above, and cannot solve the above-described problem.
[0011]
[Patent Document 1]
JP-A-63-109901 [Patent Document 2]
Japanese Patent Application Laid-Open No. 9-43542 [Patent Document 3]
Japanese Utility Model Registration No. 2508176
[Problems to be solved by the invention]
The present invention has been made in order to solve the above problems, and secures an optically effective area even when downsized, and minimizes optical foreign matter generated in an optical filter without reducing mechanical shock. It is another object of the present invention to provide a high-quality and more reliable optical filter capable of easily distinguishing a light-flux separation direction and the front and back of an optical filter main surface so as to obtain a required light-flux separation pattern.
[0013]
[Means for Solving the Problems]
Therefore, the optical filter of the present invention has a light beam separating direction in which light rays incident on the main surface are separated in a predetermined direction and emitted, and the first surface is provided on the entire periphery of at least one main surface end on the incident side or the output side. An optical filter, wherein a second chamfer having a different chamfer amount from the first chamfer indicating a light beam separation direction is formed at at least one main surface end on the entrance side or the exit side. It is characterized by being done.
[0014]
In the above-described configuration, the second chamfer is formed on only one of the front and back principal surfaces of the optical filter.
[0015]
In the above-described configuration, the optical filter is characterized in that the optical filter has a square main surface, a regular octagonal main surface, or a circular main surface.
[0016]
【The invention's effect】
According to the present invention, since the second chamfer having a different chamfer amount from the first chamfer can be used as a mark for clearly indicating the light beam separation direction, a required light beam separation pattern can be obtained.
[0017]
In addition, the chamfer mark is easier to secure an optically effective area even if it is miniaturized, and cracks and the like can be generated even when processing an optical filter, as compared with a mark formed of a conventional notch or the like. Absent.
[0018]
Further, since at least the first chamfer or the second chamfer is applied to the entire periphery of at least one main surface end on the incident side or the outgoing side of the optical filter, cracking and chipping of the optical plate can be suppressed. Thus, the mechanical impact resistance of the optical filter itself can be improved, and optical foreign matter such as cutting waste generated by contact with the case or the like can be suppressed.
[0019]
In addition, since the second chamfer is constituted by the same chamfer as the first chamfer, it can be produced extremely efficiently and inexpensively only by the chamfering step without passing through a separate step for providing a mark.
[0020]
Therefore, it is possible to provide a high quality and more reliable optical filter.
[0021]
According to the second aspect, in the case where the second chamfer is formed only on one of the front and back principal surfaces of the optical filter, in addition to the above-described operation and effect, it can be a mark for clearly discriminating the front and back of the main surface of the optical filter. In particular, when the member formed on the front surface side of the optical filter and the coating material are different from the member formed on the rear surface side of the optical filter and the coating material are different from each other, the desired optical surface can be determined by discriminating the front and back main surfaces of the optical filter. Characteristics are obtained.
[0022]
When the different members are optical low-pass filters having different separation patterns, the required light beam separation patterns can be arranged without being disturbed. When the different members and the coating material are a crystal birefringent plate and an infrared cut filter, by disposing the main surface having the infrared cut filter in a direction in which the main surface having the infrared cut filter is separated from the CCD side, as described above, the video output image quality deteriorates. It can be difficult to make it.
[0023]
According to the third aspect, in addition to the discrimination of the light beam separation direction, the discrimination between the front and back main surfaces of the optical low-pass filter or the discrimination between the vertical direction and the horizontal direction can be made even when the optical low-pass filter is rotated by 90 ° at the center point. Therefore, the present invention can be applied to an optical filter having a square surface, a regular octagonal principal surface, or a circular principal surface.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
A first embodiment of the present invention will be described with reference to the drawings, taking an optical low-pass filter as an example. FIG. 1 is a perspective view showing a first embodiment according to the present invention. FIG. 2 is a view showing a modification thereof, and FIGS. 2A to 2C are plan views on the light exit surface side, and FIG. 2D is a perspective view on the light entrance surface side. FIG. 3 is a diagram showing a manufacturing method.
[0025]
The optical low-pass filter according to the present embodiment has a single-plate configuration of a crystal birefringent plate 1 having a square main surface as shown in FIG. As is well known, the crystal birefringent plate separates incident light into an ordinary ray and an extraordinary ray by using the birefringence effect of quartz to make outgoing light, and the light separation direction and separation width are appropriately adjusted by predetermined parameters. Can be. A coating material 1a such as an infrared cut coat or a light reflection preventing coat is formed on the light incident surface (the back main surface in the figure) of the crystal birefringent plate 1. Although not shown in detail, the coating material 1a can be obtained by forming a multi-layered dielectric thin film (Al2O3, TiO2, SiO2, etc.) composed of a metal oxide film or the like.
[0026]
A first chamfer 11 is formed around a light exit surface (main surface on the front side in the figure) of the crystal birefringent plate 1 and on a side portion parallel to the light separation direction, and is orthogonal to the light separation direction. A second chamfer 12 having a larger chamfer amount than the first chamfer is formed on the side portion in the direction.
[0027]
Such a configuration clearly indicates that the optical separation direction exists in the direction in which the second chamfer 12 is formed. Further, in the case of the present embodiment, since the second chamfer is formed only on the light emitting surface, the main surface without the second chamfer is the light incident surface and the surface on which the coating material 1a is formed. If there is, the front and back can be distinguished. Furthermore, the mark for clearly indicating the direction of the light beam separation by chamfering is easier to secure an optically effective area even if it is miniaturized, compared to a mark with a conventional notch, etc. Does not occur. Further, since the edge is not formed on the side of the light exit surface side of the quartz birefringent plate 1, the generation of optical foreign matter due to cracking or chipping of the optical filter is eliminated, and the edge is packed. The generation of optical foreign matter by cutting the case or the like can be suppressed as much as possible. Further, since the second chamfer is formed opposite to two places at the end of the main surface, the chamfering in the direction orthogonal to the light beam separation direction is performed by the same dicing blade or the like according to the second chamfer amount. Since processing can be performed by a processing jig at a time, productivity is increased and manufacturing costs are suppressed.
[0028]
In addition, without being limited to the chamfering mode of the first embodiment, as shown in FIG. 2A, a portion around the light exit surface of the crystal birefringent plate 1 and parallel to the light separating direction is provided. A first chamfer 11 is formed, and a second chamfer 13 having a smaller chamfer amount than the first chamfer may be formed on a side portion in a direction orthogonal to the light separating direction. Further, as shown in FIG. 2B, the above-mentioned second chamfer is opposed to two end portions of the light exit surface of the crystal birefringent plate 1 in the direction orthogonal to the light separation direction. However, a second chamfer 14 having a larger chamfer amount than the first chamfer 11 may be formed only on a part of the edge of the main surface. Further, as shown in FIG. 2 (c), one side in the optical axis direction (the direction of the arrow in the figure) around the light exit surface of the crystal birefringent plate 1 and perpendicular to the light separation direction. The second chamfer 12 having a larger chamfer amount than the first chamfer 11 may be formed only. In this case, the vertical direction and the horizontal direction can be distinguished even if the optical low-pass filter is rotated by 90 ° at the center point of the main surface.
[0029]
Further, as shown in FIG. 2D, a first chamfer is formed around the light emitting surface (the main surface on the back side in the figure) of the crystal birefringent plate 1 and around the entire edge of the main surface. And around the light incident surface (the main surface on the front side in the figure) of the crystal birefringent plate 1 and in a direction orthogonal to the light separation direction and only one side in the optical axis direction (the direction of the arrow in the figure). In addition, a second chamfer 12 having a larger chamfer amount than the first chamfer 11 may be formed. In this case, the main surface having only the second chamfer is the light incident surface and the surface on which the coating material 1a is formed. Even if rotated, vertical and horizontal directions can be distinguished. Further, although not shown, the first chamfer may be formed on both main surfaces of the front and back surfaces, and the second chamfer may be formed only on one main surface of the front and back surfaces. In such a case, the first chamfer and the second chamfer may be formed on both front and back main surfaces.
[0030]
Next, a method of forming the chamfer will be described with reference to the schematic diagram of FIG.
As shown in FIG. 3A, a birefringent plate wafer W that separates light in the horizontal direction (arrows in the figure) is obtained.
As shown in FIG. 3B, a dielectric thin film (Al2O3, TiO2, SiO2, etc.) M made of a metal oxide film or the like is formed in multiple layers on the incident surface W1 of the wafer W by means such as a vacuum evaporation method. Such an optical filter wafer W is adhered to a support table (not shown) with a water-soluble adhesive, and predetermined small cutting is performed.
As shown in FIG. 3 (c), the blades B and C used for the small cutting are disc-shaped dicing blades, and the narrow parallel cutting portions B1 and C1 in the cross section are viewed as outer peripheral portions (outer portions). And the inside thereof have slope portions B2 and C2 corresponding to the amount of chamfering to be formed on the optical filter. The difference between the blades B and C is that the inclination angle of the slope portion is different, and the slope portion C2 has a more obtuse angle with respect to the slope portion B2.
As shown in FIG. 3 (d), the blade B corresponding to the first chamfer amount is rotated at a high speed from the exit surface side W2 of the wafer W to all cut portions in a direction parallel to the light beam separation direction. Deeply into the vicinity of the end end of.
As shown in FIG. 3 (e), the blade C corresponding to the second chamfer amount is rotated at a high speed from the exit surface side W2 of the wafer W to all cut portions in a direction orthogonal to the light beam separation direction. Deeply into the vicinity of the end end of.
As described above, the optical filter wafer W is cut into a matrix. Thereby, the cut surface of the wafer becomes the side surface of the optical filter, and the chamfer can be formed only on the main surface side of the emission surface W2 of the optical filter. Thereafter, as shown in FIG. 3F, the water-soluble adhesive is dissolved and separated into individual optical filters 1.
[0031]
The method for manufacturing an optical filter according to the present invention is not limited to the above method. For example, after cutting by the blade C, the blade may be cut by the blade B, or the first chamfer may be replaced by the blade C2 and the second chamfer may be replaced by the blade B2. Further, after only cutting the optical filter, the first chamfering and the second chamfering may be performed.
[0032]
Further, in the above manufacturing method, the first chamfer and the second chamfer amount are made different by using the blades B and C having slopes having different inclination angles, but the blades having the same slope angle are used. It can also be implemented. That is, by making the cutting depth of the blade different, the contact area between the slope portion and the wafer changes, and the chamfer amount can be made different. And the second chamfer with a large amount of chamfer can be used (these definitions can be reversed). According to this manufacturing method, it is possible to carry out the method simply by controlling the cut amount without replacing the blade, so that the manufacturing efficiency is further improved.
[0033]
Next, an optical low-pass filter according to the second embodiment will be described with reference to the drawings.
[0034]
As shown in FIG. 4, the crystal birefringent plate 2, infrared cut filter plate 3 (glass, resin plate, etc.), quarter wave plate 4 (crystal plate, resin plate, etc.), and crystal birefringent plate 5 are stacked. It is a combined configuration. As is well known, the crystal birefringent plate separates incident light into an ordinary ray and an extraordinary ray by using the birefringence effect of quartz to make outgoing light, and the light separation direction and separation width are appropriately adjusted by predetermined parameters. Can be. An optical low-pass filter is formed by appropriately combining such crystal birefringent plates and the like. The quartz birefringent plate 2 is set, for example, to separate light beams in the horizontal direction, and has a function of separating incident light in the horizontal direction by the birefringence effect of quartz. A coating material 2a such as an infrared cut coat is formed on the light incident surface of the crystal birefringent plate 2. The crystal birefringent plate 5 is set, for example, to separate light rays in the direction of 90 degrees, and has a function of separating incident light in the direction of 90 degrees by the birefringence effect of quartz. Further, a coating material 5a such as an anti-reflection coating is formed on the light emitting surface of the crystal birefringent plate 5.
[0035]
First chamfers 21 and 51 are formed around sides of the light incident surface of the crystal birefringent plate 2 and the light emitting surface of the crystal birefringent plate 5 and parallel to the light separation direction, respectively. Second chamfers 22 and 52 are formed on the side portions in the direction orthogonal to the light separation direction, the chamfers being formed larger than the first chamfer. Further, the chamfer amount of the second chamfer 52 of the crystal birefringent plate 5 is formed larger than that of the second chamfer 22 of the crystal birefringent plate 2.
[0036]
Such a configuration clearly indicates that the optical separation direction exists in the direction in which the second chamfers 22 and 52 are formed. Further, in the case of the present embodiment, since the second chamfer of the crystal birefringent plate 2 and the second chamfer amount of the crystal birefringent plate 5 are changed, it is possible to distinguish between front and back. Furthermore, the chamfer mark is easier to secure an optically effective area even if it is miniaturized, and may cause cracks and the like even when processing an optical filter, as compared with a mark formed of a conventional notch or the like. Absent. In addition, since the light incident surface side of the crystal birefringent plate 2 and the light emission surface side of the crystal birefringent plate 5 are configured so that no ridges are formed on the sides, the optical filter may be broken or chipped. The generation of foreign matter is eliminated, and the generation of optical foreign matter due to the ridge cutting the packing case or the like can be suppressed as much as possible.
[0037]
The present invention is not limited to the chamfering mode of the second embodiment, and the first chamfering and the second chamfering may be performed only on the light emitting surface of the crystal birefringent plate 5. Also, a first chamfer is formed on both sides of each optical plate (crystal birefringent plate 2 and crystal birefringent plate 5) constituting the optical filter, and a second chamfer is formed only on one side of each optical plate. Alternatively, a first chamfer and a second chamfer may be formed on both sides of each optical plate. Thereby, since the light beam separating direction and the front / back discrimination of each optical plate can be appropriately bonded to each other in a recognized state, an optical filter having a required light beam separating pattern and optical characteristics can be obtained.
[0038]
As an embodiment of the present invention, a mark indicating the light separation direction is formed by forming a second chamfer in a direction perpendicular to the light separation direction, but a second chamfer is formed in a direction parallel to the light separation direction. May be used as a mark indicating the light separation direction. Although the main surface of the optical filter has a square shape as an example, the present invention can also be applied to other main surface shapes such as a square shape. Furthermore, since the vertical direction and the horizontal direction can be distinguished even when rotated by 90 ° at the center point of the optical low-pass filter main surface, the optical filter is not limited to a square shape, but can be an optical filter having a main surface regular octagonal shape or a main surface circular shape. Is also applicable. In the above-described embodiment, an infrared cut filter is used as an example of the color correction filter. However, the present invention may be applied to an ultraviolet cut filter, a filter that cuts infrared rays and ultraviolet rays, and the like.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a first embodiment.
FIG. 2 is a plan view of a light emitting surface side showing a modification of the first embodiment.
FIG. 3 is a diagram illustrating a manufacturing method according to the first embodiment;
FIG. 4 is a perspective view showing a second embodiment.
FIG. 5 is a plan view showing a light incident surface side according to a second embodiment.
FIG. 6 is a plan view showing a light emitting surface side according to a second embodiment.
[Explanation of symbols]
1, 2, 5 crystal birefringent plate 3 infrared cut filter plate 4 1/4 wavelength plate W optical filter wafer B, C blade

Claims (3)

An optical element having a light beam separation direction in which light rays incident on a main surface are separated in a predetermined direction and emitted, and a first chamfer is applied to the entire periphery of at least one of the main surface ends on the incident side or the output side. Filter
An optical filter, wherein a second chamfer having a different chamfer amount from the first chamfer indicating a light beam separation direction is formed at an end of at least one of the main surfaces on the incident side or the output side. 2. The optical filter according to claim 1, wherein the second chamfer is formed only on one of the front and back principal surfaces of the optical filter. The optical filter according to claim 1, wherein the optical filter has a principal surface square shape, a principal surface regular octagon shape, or a principal surface circular shape.

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